HP 645A - Cyan - original - LaserJet - toner cartridge (C9731A) - for Color LaserJet 5500, 5550; LaserJet 5000. HP LaserJet printing supplies are always the right choice. They deliver exceptional print quality and hassle-free operation, page after page because they're specifically designed to work with HP's printers. Did you know that 70% of a LaserJet printer's imaging system comes from HP LaserJet print cartridges? The technology of the print cartridge is any printing system's most critical component. So if you're not using HP supplies, you're not getting HP printing. With HP LaserJet printing supplies, you also know you're getting the best total cost of ownership because Hewlett-Packard factors in qualities like reliability.